Injection molding tools are used in plastics processing. They have, in most cases, a first tool half that supplies a flowable plastic material at a predeterminable temperature and under high pressure from a first tool half to a second tool half that can be separated from the first too half (molding cavity). The first tool half usually comprises a plurality of component parts, such as, for example, a bottom plate, distributor plate, a plurality of injection molding nozzles that are connected thereto, spacers, as well as a heating device with temperature monitoring. The distributor plate has, in most cases, a feed station as well as distribution channels that are configured within the distributor plate and that feed the plastic material mass as evenly as possible to the injection molding nozzles. Each injection molding nozzle has a flow channel that is incorporated in a material pipe and flow-connected to a distribution channel in the distributor plate, and which opens into a nozzle tip at the end thereof that is oriented towards the second tool half. The injection molding nozzles are fixedly connected to the distributor, for example by a screwed or flanged connection. Additional sealing is intended to ensure a leak-proof connection between the distributor plate and the injection molding nozzles.
The problem herein lies in the fact that the complexity in assembling the first tool half is relatively high, because the injection molding nozzles are often not connected to the distributor plate until the overall tool is fastened to the distributor plate. A correspondingly large available amount of space is necessary for this step in order to be able to insert as well as fasten the nozzles in place. Moreover, assembly errors can occur that will interfere with the later production process. For example, the injection molding nozzles and the distributor plate must be braced in relation to one another in such a manner that the interface ensures a leak-proof connection even in the cold operating state. On the other hand, the screwed connection between the nozzle and the distributor plate must allow for sufficient thermal expansion to ensure that no inadmissibly high tensile forces are created that can result in a tearing off of the nozzles. Correspondingly, due to the relatively frequent temperature changes, which occur, in most cases, at high temperatures, leaks can result at the interfaces between injection molding nozzles and distributor plate.
To solve this problem, DE 40 41 532 A1 proposes incorporating the distributor plate and the injection molding nozzles that are connected thereto into one composite body. The distribution channels therein are formed in the distributor plate, and the flow channels inside the injection molding nozzles are each formed by continuous pipes that are disposed inside a metal housing. The latter is then poured out with copper or a copper alloy; the result is a composite body comprising the distributor plate and the injection molding nozzles. Moreover, heating pipes are also poured in with the copper block, whose electric connection lines are guided to a joint supply hookup. The heating pipes are intended to maintain the plastic melt, which is routed through the continuous pipes, at a constant temperature, insofar as this is possible.
Producing such a component part for a tool half of an injection molding tool is quite a complex and expensive undertaking, because, first, it is necessary to produce a substantially rectangular block-like section for the distributor plate and a plurality of cylindrical sections for the injection molding nozzles that are welded thereto. Subsequently, the continuous pipes and the heating pipes must be positioned and fixed in place inside the housing to make sure that the individual elements do not shift, when the housing is poured out.
A further disadvantage of this apparatus is the fact that the separately configured housing sections that are intended for the injection molding nozzles take up a large amount of space, wherefore it is not possible to position the individual injection molding nozzles in sufficiently close proximity relative to each other. The spaces between the molding cavities are therefore quite large. However, many areas of application call for the spaces between cavities to be as small as possible so as to be able to feed separate cavities simultaneously or complicated component parts in minimally spaced gaps multiple times.
Also disadvantageous is the fact that the heating device is poured in with the copper block. If the heater becomes damaged, said heater cannot just be disassembled and replaced with a new heater. The total component part comprising the distributor plate, injection molding nozzles, heating pipes and temperature feeler must be replaced in this instance, thus resulting in unnecessary downtimes and unfavorable effects regarding the operating costs of the injection molding apparatus.